JP2023089596A - Polyamic acid composition, polyimide, polyimide film, metal-clad laminate, production methods of these, and circuit board - Google Patents

Abstract

To provide a polyamic acid composition which, in a state of a polyamic acid solution, allows setting of molecular weight, viscosity, and solid concentration of the polyamic acid mutually in a wide range.SOLUTION: A polyamic acid composition comprises: (a) a polyamic acid obtained by reacting a tetracarboxylic acid dianhydride component including a tetracarboxylic acid dianhydride and a diamine component including a diamine compound; and (b) an organic solvent. The component (a) has ketone groups in a molecule, where the ketone groups are derived from the tetracarboxylic acid dianhydride and/or the diamine compound and a molar ratio of the tetracarboxylic acid dianhydride component and the diamine component (tetracarboxylic acid dianhydride component/diamine component) is less than 0.985.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to polyamic acid compositions, polyimides, polyimide films, metal-clad laminates, methods for producing them, and circuit boards that can be used as materials for circuit boards and the like.

Aromatic polyimides are widely used in the field of electronic materials and the like due to their high heat resistance and dimensional stability. In Patent Document 1, as an insulating resin layer of a flexible printed circuit board (FPC; Flexible Printed Circuits), it is derived from a tetracarboxylic dianhydride having a high storage modulus and a ketone group (-CO-) in the molecule. A polyimide containing a predetermined amount of acid dianhydride residues has been proposed. In addition, Patent Document 2 proposes the use of polyimide, which contains specific structural units and has increased tear propagation resistance, as an insulating resin layer for FPCs and HDD suspensions.

Since aromatic polyimides are insoluble and infusible in solvents, a two-step synthesis method is often used in which a solution of polyamic acid, which is a precursor, is prepared, a film is formed, and imidized by heat treatment to form a film. In the case of the polyimide film produced by the two-step synthesis method, the molecular weight of the polyimide after imidization is almost uniquely determined by the molecular weight of the precursor polyamic acid. In general, not only polyimide but also other high-molecular-weight compounds tend to yield tougher films as the molecular weight increases. However, since the solution of polyamic acid with a high molecular weight becomes viscous, when considering the film-forming property, the degree of freedom of the viscosity and solid content concentration of the polyamic acid solution with respect to the molecular weight of the polyamic acid is limited. I had a problem. For example, when producing a thick film, a high solid content concentration is advantageous for coating, but if the molecular weight of polyamic acid is increased to increase the film strength, the viscosity at a high solid content concentration will increase too much, becomes difficult. On the other hand, in the case of producing a thin film, if a polyamic acid solution with a large molecular weight is to be adjusted to have a low viscosity, the solid content concentration must be greatly reduced, which can be a factor in the deterioration of the film formability. By lowering the molecular weight of the polyamic acid, the above problems of coatability and film-forming properties can be solved, but sufficient film strength cannot be obtained.

Thus, in the production of an aromatic polyimide film, the viscosity and solid content concentration of the polyamic acid solution must be adjusted to an appropriate range according to the molecular weight of the polyamic acid. Considering this, there was a limit to the range of adjustment when making the viscosity low or making the solids concentration high. From another point of view, when the viscosity and solid content concentration of the polyamic acid solution are set with priority given to coatability and film-forming properties, the molecular weight of polyamic acid is restricted, and a high-molecular-weight, high-strength aromatic polyimide film is produced. There was a problem that it became difficult.

Japanese Patent Application Laid-Open No. 2020-104340 Japanese Patent No. 5009714

Therefore, the first object of the present invention is to provide a polyamic acid composition in which the molecular weight, viscosity, and solid content concentration of polyamic acid can be set widely in the state of a polyamic acid solution. An object is to provide a polyimide film having a high molecular weight and high strength by using the polyamic acid composition.

The present inventors introduced a specific functional group into the polyamic acid and controlled the ratio of the tetracarboxylic dianhydride component and the diamine component as raw materials, thereby improving the viscosity and the molecular weight of the polyamic acid. The inventors have found that it is possible to obtain a polyamic acid composition whose solid content concentration can be set over a wide range, and have completed the present invention.

That is, the polyamic acid composition of the present invention comprises the following components (a) and (b);
(a) a polyamic acid obtained by reacting a tetracarboxylic dianhydride component containing a tetracarboxylic dianhydride and a diamine component containing a diamine compound;
(b) an organic solvent,
contains In the polyamic acid composition of the present invention, the component (a) has a ketone group in its molecule, and the ketone group is derived from the tetracarboxylic dianhydride and/or the diamine compound. ,
The molar ratio of the tetracarboxylic dianhydride component to the diamine component (tetracarboxylic dianhydride component/diamine component) is less than 0.985.

In the polyamic acid composition of the present invention, the polyamic acid may have a weight average molecular weight (Mw) of 10,000 or more and 500,000 or less.

In the polyamic acid composition of the present invention, the content of ketone groups in the component (a) is 5 mol parts or more per 100 mol parts in total of the acid dianhydride residue and the diamine residue. good too.

The polyimide of the present invention is obtained by reacting a tetracarboxylic dianhydride component containing a tetracarboxylic dianhydride and a diamine component containing a diamine compound. In the polyimide of the present invention, the molar ratio of the tetracarboxylic dianhydride component and the diamine component (tetracarboxylic dianhydride component/diamine component) is less than 0.985, and the tetracarboxylic dianhydride and/or an imine bond formed by a ketone group derived from the diamine compound and an amino group derived from the diamine compound.

The polyimide film of the present invention contains the above polyimide as a main component of the resin component.

The metal-clad laminate of the present invention is a metal-clad laminate comprising an insulating resin layer and a metal layer laminated on one side or both sides of the insulating resin layer, wherein the insulating resin layer comprises the polyimide A film is included.

The method for producing a polyimide film of the present invention comprises the following steps I and II;
I) a step of applying the polyamic acid composition onto a substrate and drying to form a coating film of polyamic acid;
II) a step of heat-treating the coating film to imidize the polyamic acid to form a polyimide film;
includes.

The method for producing a metal-clad laminate of the present invention comprises the following steps i and ii;
i) a step of applying the polyamic acid composition onto a substrate containing a metal foil and drying to form a coating film of polyamic acid;
ii) heat-treating the coating film on a substrate containing a metal foil to imidize the polyamic acid to form a polyimide layer;
includes.

Furthermore, the present invention provides a circuit board in which the metal layer of the metal-clad laminate described above is processed into wiring.

In the polyamic acid composition of the present invention, the molecular weight, viscosity, and solid content concentration of the polyamic acid can be set in a wide range. A variety of different polyimide films can be formed. In particular, when forming a polyimide film having a high molecular weight and a high strength, it is industrially advantageous because the adjustment range of the viscosity and solid content concentration of the polyamic acid composition can be widened.

BRIEF DESCRIPTION OF THE DRAWINGS It is drawing which shows the relationship between the weight average molecular weight (horizontal axis) in a general aromatic polyamic acid, and the tear propagation resistance (vertical axis) of a polyimide film. A drawing showing the relationship between the molar ratio (horizontal axis) of the tetracarboxylic dianhydride component and the diamine component in the aromatic polyamic acids of Examples, Reference Examples, and Comparative Examples, and the tear propagation resistance (vertical axis) of the polyimide film. be. BRIEF DESCRIPTION OF THE DRAWINGS It is drawing which shows the relationship between the weight average molecular weight (horizontal axis) in the aromatic polyamic acid of an Example, a reference example, and a comparative example, and the tear propagation resistance (vertical axis) of a polyimide film.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate.

[Polyamic acid composition]
A polyamic acid composition according to one embodiment of the present invention comprises the following components (a) and (b);
(a) a polyamic acid obtained by reacting a tetracarboxylic dianhydride component containing a tetracarboxylic dianhydride and a diamine component containing a diamine compound, and (b) an organic solvent,
contains

(Component (a): polyamic acid)
The component (a) polyamic acid has a ketone group (--CO--) in its molecule. The ketone group is derived from tetracarboxylic dianhydride and/or diamine compound, which are raw materials of polyamic acid. That is, polyamic acid contains an acid dianhydride residue and a diamine residue, and either or both of the acid dianhydride residue or the diamine residue contains a residue having a ketone group. ing. In the present invention, the term "acid dianhydride residue" refers to a tetravalent group derived from a tetracarboxylic dianhydride, and the term "diamine residue" refers to a divalent group derived from a diamine compound. represents the group of When the tetracarboxylic dianhydride component containing the tetracarboxylic dianhydride and the diamine component containing the diamine compound as raw materials are reacted in approximately equimolar amounts, the polyimide contains The types and molar ratios of the acid dianhydride residues and diamine residues contained can be substantially matched.
In addition, in the "diamine compound", hydrogen atoms in two terminal amino groups may be substituted.

Acid dianhydride residues having a ketone group include, for example, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 2,3′,3,4′-benzophenonetetracarboxylic dianhydride. , 2,2′,3,3′-benzophenonetetracarboxylic dianhydride, 4,4′-(paraphenylene dicarbonyl) diphthalic anhydride, 4,4′-(metaphenylene dicarbonyl) diphthalic anhydride and residues derived from "a tetracarboxylic dianhydride having a ketone group in the molecule".

Acid dianhydride residues other than acid dianhydride residues having a ketone group include, for example, those shown in the examples below, and those derived from tetracarboxylic dianhydrides generally used in the synthesis of polyimides. and acid dianhydride residues. However, from the viewpoint of storage stability of the polyamic acid composition, the acid dianhydride residue preferably consists only of an aromatic dianhydride residue derived from an aromatic tetracarboxylic acid compound.

Diamine residues having a ketone group include, for example, 3,3′-diaminobenzophenone, 3,4′-diaminobenzophenone, 4,4′-diaminobenzophenone, 4,4′-bis[4-(4-amino- α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4′-bis(4-aminophenoxy)benzophenone, 4,4′-bis(3-aminophenoxy)benzophenone (BABP), 1,3-bis[4- (3-Aminophenoxy)benzoyl]benzene (BABB), 1,4-bis(4-aminobenzoyl)benzene, 1,3-bis(4-aminobenzoyl)benzene, etc. "Diamine compounds having a ketone group in the molecule can be mentioned.

Examples of the diamine residue other than the diamine residue having a ketone group include those shown in the examples below, as well as diamine residues derived from diamine compounds generally used in polyimide synthesis. However, from the viewpoint of storage stability of the polyamic acid composition, the diamine residue does not contain an aliphatic diamine residue derived from an aliphatic diamine compound, and an aromatic diamine residue derived from an aromatic diamine compound. It is preferable to consist only of

The amount of ketone groups present in the polyamic acid (as -CO-) is preferably 5 mol parts or more with respect to the total 100 mol parts of the acid dianhydride residue and the diamine residue, and 10 to 50 It is more preferably within the mole part range. If the content of the ketone group present in the polyamic acid is less than 5 mol parts, the imination reaction during thermal imidization may not proceed sufficiently, and the desired film strength may not be obtained. The upper limit of the amount of the ketone group is not particularly limited, but it is preferably 50 mol parts or less with respect to the total 100 mol parts of the acid dianhydride residue and the diamine residue. increase, making it easier to control physical properties.

In the present embodiment, as the polyamic acid, preferably a polyamic acid having most of the terminals with amino groups, more preferably a polyamic acid having all of the terminals with amino groups is used. Thus, a polyamic acid rich in amino termini can be formed by adjusting the molar ratio of both components so that there is an excess of the diamine component relative to the tetracarboxylic dianhydride component in the starting material. Specifically, the molar ratio of the tetracarboxylic dianhydride component and the diamine component (tetracarboxylic dianhydride component/diamine component) is less than 0.985, preferably within the range of 0.930 to 0.980, more By adjusting the range preferably within the range of 0.970 to 0.980, the majority of the polyamic acid synthesized can be polyamic acid with amino termini (—NH ₂ ). When the molar ratio of the tetracarboxylic dianhydride component and the diamine component is less than 0.985, the polyamic acid has a low molecular weight, and it is thought that the film after imidation tends to become brittle. It is possible to increase the molecular weight at the stage of polyimide due to the imine reaction during polyimide, and the strength of the film can be sufficiently increased. Thus, when the molar ratio of the tetracarboxylic dianhydride component and the diamine component is less than 0.985, the effects of the present invention are remarkably exhibited. When the ratio of the tetracarboxylic dianhydride component to 1 mol of the diamine component is 0.985 mol or more, the polyamic acid itself has a high molecular weight. Since a tough film is often obtained after curing, the effects of the invention are difficult to manifest. On the other hand, if the ratio of the tetracarboxylic dianhydride component to the diamine component is too small, the high molecular weight polyamic acid will not proceed sufficiently. Therefore, the charged molar ratio of the tetracarboxylic dianhydride component to 1 mol of the diamine component is, for example, 0.930 or more, preferably in the range of 0.930 to 0.980, more preferably 0.970 to 0.980. should be within the range.

(Synthesis of polyamic acid)
A polyamic acid can be produced by reacting the tetracarboxylic dianhydride component and the diamine component in a solvent. For example, the tetracarboxylic dianhydride component and the diamine component are dissolved in an organic solvent at the above molar ratio, and stirred at a temperature within the range of 0 to 100 ° C. for 30 minutes to 24 hours for polymerization reaction to produce polyamic acid. can get. In the reaction, it is preferable to dissolve the reaction components in the organic solvent so that the polyamic acid produced is within the range of 5 to 30% by weight, preferably within the range of 10 to 20% by weight. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2 -butanone, dimethylsulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, cresol and the like. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. The amount of such an organic solvent used is not particularly limited, but the amount used is adjusted so that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 30% by weight. is preferred.
Since the polyamic acid synthesized generally has excellent solvent solubility, it is usually advantageous to use it as a reaction solvent solution, but if necessary, it can be concentrated, diluted, or replaced with another organic solvent.

In the synthesis of polyamic acid, each of the tetracarboxylic dianhydride and the diamine compound may be used alone or in combination of two or more. By selecting the types of tetracarboxylic dianhydride and diamine compound, and the respective molar ratios when using two or more tetracarboxylic dianhydrides or diamine compounds, the elastic modulus of polyimide, mechanical strength, Physical properties such as thermal expansibility, adhesiveness, and glass transition temperature can be controlled.
When the polyamic acid of the present embodiment has a plurality of structural units, they may be present as blocks or randomly, but are preferably present randomly. The same applies to polyimide to be described later.

(Weight average molecular weight of polyamic acid)
The weight average molecular weight (Mw) of the polyamic acid is preferably in the range of 10,000 or more and 500,000 or less, and the Mw may be appropriately adjusted within this range depending on the purpose. If the Mw is less than 10,000, the strength of the film is lowered and the film tends to become brittle. On the other hand, if the weight-average molecular weight exceeds 500,000, the viscosity increases and defects such as uneven film thickness and streaks tend to occur during coating.

(Component (b): organic solvent)
As the organic solvent of component (b), the same organic solvent as used in the polymerization reaction can be used. Thus, for example, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethylsulfoxide (DMSO ), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, cresol and the like. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination.
Although the content of the organic solvent in the polyamic acid composition is not particularly limited, it is preferable that the concentration of the polyamic acid is about 5 to 30% by weight.

(Optional component)
The polyamic acid composition of the present embodiment includes optional components such as an organic filler, an inorganic filler, a cyclizing agent, an imidization catalyst, a curing agent, a plasticizer, an elastomer, a coupling agent, a pigment, a flame retardant, and a heat radiation agent. etc. can be contained.

[Polyimide]
The polyimide of the present embodiment is obtained by imidating the precursor polyamic acid having the above structure. The method for imidating polyamic acid is not particularly limited, and for example, a heat treatment such as heating at a temperature within the range of 80 to 400° C. for several minutes to 24 hours is preferably employed.
In the present invention, the term "polyimide" means a resin made of a polymer having an imide group in its molecular structure, such as polyamideimide, polyetherimide, polyesterimide, polysiloxaneimide, and polybenzimidazoleimide, in addition to polyimide. .

The polyimide of the present embodiment is obtained by reacting a tetracarboxylic dianhydride component containing a tetracarboxylic dianhydride and a diamine component containing a diamine compound in the same manner as polyamic acid. It contains an acid dianhydride residue derived from an anhydride and a diamine residue derived from a diamine compound. The molar ratio of the tetracarboxylic dianhydride component and the diamine component (tetracarboxylic dianhydride component/diamine component) of the raw materials is also the same as that of the polyamic acid.

Further, the polyimide of the present embodiment has an imine bond formed by a ketone group derived from a tetracarboxylic dianhydride and/or a diamine compound and an amino group derived from a diamine compound. Since this imine bond forms a branched chain with respect to the main chain of the imide bond of polyimide, Mw is greatly increased compared to polyamic acid.

The polyimide of this embodiment may be either thermoplastic polyimide or non-thermoplastic polyimide. Thermoplastic polyimide is preferable when flexibility and adhesiveness are important, such as when the polyimide of the present embodiment is used as an adhesive layer with a metal foil or other resin layer. When applied as an adhesive layer, the high film strength makes it difficult for cohesive failure to occur, and excellent peel strength can be exhibited.
On the other hand, when the polyimide of the present embodiment is applied as the main layer (base layer) of the insulating resin layer in the polyimide film or metal-clad laminate, when the function of ensuring mechanical strength is emphasized, the non-thermal A plastic polyimide is preferred. When applied as a base layer, the high film strength can provide excellent mechanical properties such as self-supporting properties, bending resistance, and impact resistance.
Whether the polyimide of the present embodiment is a thermoplastic polyimide or a non-thermoplastic polyimide can be designed depending on the kind, combination, molar ratio, etc. of the tetracarboxylic dianhydride and diamine compound used as raw materials.
The term "thermoplastic polyimide" generally refers to a polyimide whose glass transition temperature (Tg) can be clearly identified. A polyimide having a storage modulus of 1.0×10 ⁹ Pa or more at 300° C. and less than 1.0×10 ⁸ Pa at 300° C. In addition, "non-thermoplastic polyimide" generally refers to polyimide that does not soften or exhibit adhesiveness when heated. A polyimide having a storage modulus of 1.0×10 ⁹ Pa or more at 100° C. and a storage modulus of 1.0×10 ⁸ Pa or more at 300° C.

[Action]
In the polyimide of the present embodiment, imine bonding is presumed to occur between the ketone group contained in the polyamic acid and the terminal amino group due to heat treatment during imidization of the polyamic acid. In other words, the polyamic acid of the present embodiment has a molar ratio of the raw material tetracarboxylic dianhydride component and the diamine component (tetracarboxylic dianhydride component/diamine component) of less than 0.985. has an amino group at its end. Therefore, it is considered that a dehydration condensation reaction is caused by heating between the ketone group in the polyamic acid and the terminal amino group, and an imine bond is formed in the polyimide. As a result, a large number of branched chains due to imine bonds are formed in the main chain of polyimide, and the Mw of polyimide greatly increases compared to that of polyamic acid. A model of branched chain formation by such imine bond is shown below. In the model below, all of the acid anhydride residues are BTDA residues derived from 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA). It may contain other acid dianhydride residues.

In the formula, R means the same or different kind of diamine residue, and m and n mean integers indicating the number of repetitions. Moreover, (a) shows a polyamic acid that becomes a branched chain by imine bond, and (b) shows a polyamic acid that becomes a main chain of a polyimide chain.

Due to such a phenomenon, in the polyamic acid/polyimide of the present embodiment, when forming a polyimide having a certain Mw, it is possible to keep the Mw low at the polyamic acid stage, and as a result, the conventional polyamic acid/polyimide Compared to polyimide, the adjustable range of the viscosity of the polyamic acid solution has been expanded in the direction of suppressing it, and in the direction of increasing the solid content concentration.

As a polyimide having an imine bond, a technique is known in which a polyimide having a ketone group is reacted with a diamino compound such as dihydrazide to form an imine crosslinked structure. Although there is a possibility of plasticization by the agent and brittleness due to too high cross-linking density, the present invention does not have such adverse effects.

Next, FIG. 1 shows the relationship between Mw (horizontal axis) in a general aromatic polyamic acid and the tear propagation resistance (vertical axis) of a polyimide film obtained by imidizing this. FIG. 1 shows two types of polyamic acid/polyimide films, but as a general trend, it is understood that as the Mw of the polyamic acid increases, the tear propagation resistance of the polyimide film gradually increases. . In general, the molar ratio of the tetracarboxylic dianhydride component and the diamine component (tetracarboxylic dianhydride component/diamine component), which are raw materials, is closer to 1, which is advantageous for increasing the Mw of the polyamic acid. .

On the other hand, in the polyamic acid/polyimide of the present embodiment, the molar ratio of the tetracarboxylic dianhydride component and the diamine component (tetracarboxylic dianhydride component/diamine component), which are raw materials, is intentionally set to 0.985. Therefore, even if the molecular weight of polyamic acid is designed to be small, many branched chains are formed by the imine bonds that occur with the imidization reaction, so the molecular weight of polyimide can be significantly increased compared to polyamic acid. . Therefore, as shown in the examples below, the molecular weight of the polyamic acid can be designed to be lower than before in order to obtain a polyimide film having the target tear propagation resistance. In other words, in order to obtain a polyimide film having a target strength, it is possible to widen the adjustment range in the direction of decreasing the Mw of the polyamic acid as compared with the conventional technology. Therefore, the following applications are possible.

In the polyamic acid/polyimide of the present embodiment, an increase in viscosity (Mw of polyamic acid) of the polyamic acid composition can be suppressed even if the solid content concentration is increased. For example, when producing a relatively thick polyimide film having a thickness of about 50 to 200 μm, even if a high solid content concentration of about 15 to 20% by weight, which is advantageous for coating, is selected, the viscosity of the polyamic acid composition is reduced. It can be controlled to about 2,000 to 50,000 cP. On the other hand, since the Mw after imidization can be made sufficiently larger than the Mw of polyamic acid, a high-strength polyimide film can be produced. Such thick and high-strength polyimide films are extremely useful for, for example, circuit boards, strip lines, microstrip lines, RF cables, insulating materials, coating materials, heat insulating materials, polyimide heaters, etc. that transmit high-frequency signals after 5G. be.

Moreover, the viscosity of the polyamic acid composition can be lowered (the Mw of the polyamic acid can be lowered) without lowering the solid content concentration. For example, when producing a relatively thin polyimide film having a thickness of about 3 to 15 μm, even if a low viscosity of about 500 to 10,000 cP that is advantageous for coating is selected, a high solid content concentration of the polyamic acid composition can be controlled to about 10 to 18% by weight. On the other hand, since the Mw after imidization can be made sufficiently larger than the Mw of the polyamic acid, a high-strength polyimide film can be produced without deteriorating the film formability. Such a thin and high-strength polyimide film is extremely useful, for example, for space-saving circuit boards such as FPCs, for miniaturization, heat dissipation materials, polyimide tubes, and the like.

As described above, in the polyamic acid composition of the present invention, the molecular weight, viscosity, and solid content concentration of the polyamic acid can be set in a wide range. Depending on the conditions, various polyimide films having different Mw, film thickness, etc. can be formed. In particular, when forming a polyimide film having a high molecular weight and high strength, the adjustment range of the viscosity and solid content concentration of the polyamic acid composition can be widened, which is advantageous in the production of a polyimide film on an industrial scale.

[Polyimide film]
The polyimide film of the present embodiment contains the polyimide having the above structure as the main component of the resin component. Here, the "main component of the resin component" means a component contained in an amount exceeding 50% by weight with respect to the total resin component. The polyimide film preferably contains 70% by weight or more, more preferably 80% by weight or more, of the polyimide having the above structure with respect to the total resin components, and most preferably all of the resin components are composed of the polyimide having the above structure. preferable. In addition, the polyimide film of the present embodiment may have a structure in which any polyimide layer is laminated.

The polyimide film of this embodiment can be produced by carrying out a method including the following steps I and II.

I) A step of applying the polyamic acid composition onto a substrate and drying to form a coating film of polyamic acid.
In step I, the substrate is not particularly limited, and for example, a metal foil such as copper foil, a glass plate, a resin film such as a polyimide film, a polyamide film, a polyester film, or a laminate thereof can be used. can. Moreover, the method of applying the polyamic acid composition is not particularly limited, and for example, it can be applied by a coater such as a comma, die, knife, or lip coater.

II) A step of heat-treating the coating film to imidize the polyamic acid to form a polyimide film.
In step II, the heat treatment conditions can be the same as those for polyimide synthesis described above. In step II, the coating film may be peeled off from the substrate before the heat treatment, and the heat treatment may be performed in the state of a polyamic acid gel film, but the heat treatment is performed on the substrate to imidize the polyamic acid. is preferably completed. In this case, since the polyamic acid resin layer is imidized in a state of being fixed to the supporting base material, it is possible to suppress the expansion and contraction change of the polyimide layer during the imidization process and maintain the thickness and dimensional accuracy of the polyimide film. can. When the heat treatment is performed on the substrate, the process of peeling the polyimide film from the substrate can be further included.

[Metal clad laminate]
The metal-clad laminate of the present embodiment includes an insulating resin layer and a metal layer laminated on one side or both sides of the insulating resin layer, and the insulating resin layer is a polyimide layer made of the above polyimide film. includes. The insulating resin layer may contain any resin layer other than the polyimide layer formed of the polyimide film.

A metal foil can be preferably used as the metal layer. The material of the metal foil is not particularly limited, but examples include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and these. and the like. Among these, copper or a copper alloy is particularly preferable. The copper foil may be a rolled copper foil or an electrolytic copper foil, and a commercially available copper foil can be preferably used.

In this embodiment, the thickness of the metal layer when used for manufacturing FPC, for example, is preferably in the range of 3 to 50 μm, more preferably in the range of 5 to 30 μm.

The surface of the metal foil used as the metal layer may be subjected to surface treatments such as antirust treatment, siding, aluminum alcoholate, aluminum chelate, silane coupling agent, and the like. In addition, the metal foil can be in the shape of a cut sheet, a roll, or an endless belt. In order to obtain productivity, it is possible to use the shape of a roll or an endless belt for continuous production. format is efficient. Furthermore, from the viewpoint of exhibiting a greater effect of improving the accuracy of the wiring pattern on the circuit board, the metal foil is preferably in the form of a long roll.

A metal-clad laminate can be produced by carrying out a method including steps i and ii below.
i) A step of applying the above polyamic acid composition onto a substrate containing a metal foil and drying to form a coating film of polyamic acid.
ii) a step of heat-treating the coating film on a substrate containing a metal foil to imidize the polyamic acid to form a polyimide layer;

Steps i and ii can be carried out in the same manner as steps I and II of the method for producing a polyimide film, except that a substrate containing a metal foil is used and imidization is completed on the substrate. Here, the "base material containing a metal foil" means a single metal foil, a laminate of a metal foil and a resin film, a laminate of a metal foil and a polyamic acid coating film, and the like.

[Circuit board]
The metal-clad laminate of the present invention is useful as a material for circuit boards such as FPC, and a circuit board produced by processing the metal-clad laminate of the present invention is also an aspect of the present invention. This circuit board can be manufactured by patterning the metal layer of the metal-clad laminate obtained by the manufacturing method of the metal-clad laminate by a conventional method to form a wiring layer. Patterning of the metal layer can be performed by any method using, for example, photolithographic techniques and etching. In addition, when manufacturing a circuit board, as processes normally performed, for example, through-hole processing in the pre-process and terminal plating and external shape processing in the post-process can be performed according to the usual methods.

EXAMPLES Examples are given below to more specifically describe the features of the present invention. However, the scope of the present invention is not limited to the examples. In the following examples, unless otherwise specified, various measurements and evaluations are as follows.

[Measurement of viscosity]
The viscosity at 25° C. was measured using an E-type viscometer (manufactured by Brookfield, trade name: DV-II+Pro). The number of revolutions was set so that the torque was 10% to 90%, and after 2 minutes from the start of the measurement, the value was read when the viscosity stabilized.

[Measurement of weight average molecular weight]
It was measured by gel permeation chromatography (manufactured by Tosoh Corporation, trade name: HLC-8420GPC). Polystyrene was used as a standard substance, and N,N-dimethylacetamide was used as an eluent.

[Measurement of coefficient of thermal expansion (CTE)]
Using a thermomechanical analyzer (manufactured by Hitachi High-Tech Science, trade name: TMA6100), the temperature was raised from 30 ° C. to 270 ° C. at a constant heating rate, held at that temperature for 10 minutes, and then increased at 5 ° C./min. It was cooled at a high speed, and the average thermal expansion coefficient (thermal expansion coefficient) from 250°C to 100°C was determined.

[Measurement of glass transition temperature (Tg) and storage modulus]
A dynamic viscoelasticity measuring device (DMA: RSA-G2, manufactured by TA Instruments) was used to measure the temperature from 30° C. to 400° C. at a rate of 5° C./min and a frequency of 1 Hz. The glass transition temperature was obtained from the temperature of the loss modulus maximum value based on the principal dispersion.

[Measurement of tensile modulus]
It was measured using a tension compression tester (manufactured by Toyo Seiki Seisakusho, trade name: Strograph R-1). The tensile modulus was calculated from the slope of the stress-displacement curve obtained by pulling at a chuck-to-chuck distance of 101.6 mm and a sweep speed of 10 mm/min.

[Measurement of tear propagation resistance]
A test piece having a length of 63.5 mm and a width of 50 mm was prepared, a cut having a length of 12.7 mm was made in the test piece, and measurement was performed using a light load tear tester manufactured by Toyo Seiki Co., Ltd.

[Measurement of peel strength]
A sample was prepared by circuit-processing the copper foil of a flexible copper-clad laminate to a width of 1.0 mm, the surface of the polyimide layer was fixed to an aluminum plate with double-sided tape, and a Tensilon tester (manufactured by Toyo Seiki Seisakusho, trade name; Graph VE-1D). The copper foil was pulled in the direction of 180 degrees at a speed of 50 mm/min, and the median strength was obtained when the peel was peeled off by 10 mm.

The abbreviations used in Examples and Comparative Examples represent the following compounds.
PMDA: pyromellitic dianhydride BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TPE-R: 1,3-bis(4-aminophenoxy)benzene DMAc: N,N-dimethylacetamide

(Synthesis example 1)
21.43 parts by weight of m-TB (100.92 mol parts) was added to 255.0 parts by weight of DMAc and stirred at room temperature for 30 minutes or more to dissolve completely. Next, 16.26 parts by weight of PMDA (74.56 mol parts) and 7.31 parts by weight of BPDA (24.85 mol parts) were added and stirred at room temperature for 4 hours to give a viscosity of 27,400 cP and a weight average A polyamic acid solution A having a molecular weight of 117,000 was obtained.

[Example 1]
10.62 parts by weight of TPE-R (36.33 parts by weight) and 7.71 parts by weight of m-TB (36.33 parts by weight) were added to 264.0 parts by weight of DMAc and left at room temperature until completely dissolved. was stirred. Next, 6.85 parts by weight of BTDA (21.25 mol parts) and 10.82 parts by weight of PMDA (49.59 mol parts) were added and stirred at room temperature for 4 hours to give a viscosity of 700 cP and a weight average molecular weight of 101. ,000 of polyamic acid solution 1 was obtained.
Polyamic acid solution 1 was evenly coated on a copper foil so that the thickness after curing was about 25 μm, and then dried by heating at 140° C. or lower to remove the solvent. Further, the temperature was raised stepwise from 140° C. to 360° C. and heat treatment was performed to complete imidization. Table 1 shows the physical properties of the obtained polyimide film 1.
Polyamic acid solution 1 was applied on a copper foil (electrolytic copper foil, thickness: 12 μm, ten-point average roughness Rz: 1 μm) so that the thickness after curing was 2 μm, and then dried by heating at 140 ° C. or less. , the solvent was removed. Polyamic acid solution A was applied thereon to a thickness of 21 μm after curing, and then dried by heating at 140° C. or lower to remove the solvent. Further, the polyamic acid solution 1 was applied thereon so that the thickness after curing was 2 μm, and then dried by heating at 140° C. or lower to remove the solvent. After that, imidization was performed by raising the temperature stepwise from 140° C. to 360° C., and a single-sided copper-clad laminate 1 was obtained. The obtained single-sided copper-clad laminate 1 was subjected to circuit processing and measured to have a peel strength value of 0.9 kN/m.

[Example 2]
Polyamic acid solution 2, polyimide film 2, and single-sided copper-clad laminate 2 were obtained in the same manner as in Example 1 except that the composition ratios shown in Table 1 were used. Table 1 shows each physical property.

[Reference Examples 1 to 3, Comparative Examples 1 to 3]
Polyamic acid solutions 3 to 8, polyimide films 3 to 8, and single-sided copper-clad laminates 3 to 8 were obtained in the same manner as in Example 1 except that the composition ratios shown in Table 1 were used. Table 1 shows each physical property.

From Table 1, although Examples 1 and 2 had a lower Mw of the polyamic acid than Reference Examples 1-3, they exhibited tear propagation resistance and peel strength equivalent to those of Reference Examples 1-3. From this, it can be seen that cohesive failure is less likely to occur in Examples 1 and 2 due to the high film strength.

The molar ratio of the tetracarboxylic dianhydride component and the diamine component (tetracarboxylic dianhydride component / diamine component) and tearing of the polyimide film in Examples 1 and 2, Reference Examples 1 to 3 and Comparative Examples 1 to 3 The relationship with propagation resistance is shown in FIG. 2, and the relationship between Mw of polyamic acid and tear propagation resistance of polyimide film is shown in FIG. 2 and 3, "Example 1", "Reference 1", "Comparison 1", etc. mean the corresponding "Example", "Reference Example", "Comparative Example" and their numbers, respectively. .

From FIG. 2, in Comparative Examples 1 to 3, when the molar ratio of the tetracarboxylic dianhydride component and the diamine component (tetracarboxylic dianhydride component/diamine component) exceeds 1, tearing occurs as the molar ratio increases. Propagation resistance is reduced. On the other hand, in Examples 1 and 2, even if the molar ratio is less than 0.985, tear propagation resistance equivalent to Reference Examples 1 to 3, in which the molar ratio is around 1, is exhibited.
On the other hand, from FIG. 3, although the polyamic acid Mw is lower than that of Reference Examples 1 to 3, in Examples 1 and 2, tear propagation resistance equivalent to that of Reference Examples 1 to 3 is exhibited. Recognize. From the above results, it is considered that in Examples 1 and 2, tear propagation resistance equivalent to that of Reference Examples 1 to 3 was developed by increasing the molecular weight of the polyimide due to the imine reaction during thermal imidization.
The results of Comparative Examples 1 to 3 in FIG. 3 are consistent with FIG. 1 above, and when the molar ratio of the tetracarboxylic dianhydride component and the diamine component exceeds 1, the polyamic acid Mw It is shown that the tear propagation resistance of the polyimide film also gradually increases as the σ increases.

Although the embodiments of the present invention have been described in detail for purposes of illustration, the present invention is not limited to the above embodiments.

Claims (9)

Components (a) and (b) below;
(a) a polyamic acid obtained by reacting a tetracarboxylic dianhydride component containing a tetracarboxylic dianhydride and a diamine component containing a diamine compound;
(b) an organic solvent,
A polyamic acid composition containing
The component (a) has a ketone group in its molecule, and the ketone group is derived from the tetracarboxylic dianhydride and/or the diamine compound,
A polyamic acid composition, wherein the molar ratio of the tetracarboxylic dianhydride component to the diamine component (tetracarboxylic dianhydride component/diamine component) is less than 0.985. 2. The polyamic acid composition according to claim 1, wherein the polyamic acid has a weight average molecular weight (Mw) of 10,000 or more and 500,000 or less. The polyamic acid according to claim 1 or 2, wherein the content of ketone groups in component (a) is 5 mol parts or more per 100 mol parts in total of the acid dianhydride residue and the diamine residue. Composition. A polyimide obtained by reacting a tetracarboxylic dianhydride component containing a tetracarboxylic dianhydride and a diamine component containing a diamine compound,
The molar ratio of the tetracarboxylic dianhydride component and the diamine component (tetracarboxylic dianhydride component/diamine component) is less than 0.985, and the tetracarboxylic dianhydride and/or the diamine compound A polyimide having an imine bond formed by a ketone group derived from the diamine compound and an amino group derived from the diamine compound. A polyimide film containing the polyimide according to claim 4 as a main component of the resin component. A metal-clad laminate comprising an insulating resin layer and a metal layer laminated on one side or both sides of the insulating resin layer,
A metal-clad laminate, wherein the insulating resin layer contains the polyimide film according to claim 5 . Step I and Step II below;
I) a step of applying the polyamic acid composition according to any one of claims 1 to 3 onto a substrate and drying to form a coating film of polyamic acid;
II) a step of heat-treating the coating film to imidize the polyamic acid to form a polyimide film;
A method for producing a polyimide film comprising: step i and step ii below;
i) a step of applying the polyamic acid composition according to any one of claims 1 to 3 onto a substrate containing a metal foil and drying to form a coating film of polyamic acid;
ii) heat-treating the coating film on a substrate containing a metal foil to imidize the polyamic acid to form a polyimide layer;
A method for producing a metal-clad laminate comprising: A circuit board in which the metal layer of the metal-clad laminate according to claim 6 is processed into wiring.

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